Syria accused Turkey on Thursday of playing a “fundamental role” in supporting terrorism by opening its airport and border to al-Qaeda and other jihadists to carry out attacks inside Syria.

“The Turkish government has set up on its soil military offices where Israeli, American, Qatari and Saudi intelligence agencies direct the terrorists in their war on the Syrian people,” Syria’s foreign ministry said in a statement circulated on state television.

Once close allies, the two countries’ relationship quickly deteriorated as President Bashar al-Assad intensified a crackdown in a 17-month-old uprising against his rule.

As many as 94 people have been killed by the fire of Syrian forces across the country, Al Arabiya reported citing Syrian activists.

Turkish Prime Minister Tayyip Erdogan has called on Assad to leave and Ankara has set up a sprawling refugee camp along the border which houses thousands of Syrian refugees.

Several military officers have defected to Turkey and the nominal commander of the Free Syrian Army, a loosely coordinated group of insurgents fighting Assad's forces, is also based there.

Damascus also accused France and the United States of sending rebels communications equipment. U.S. sources have said President Barack Obama signed a secret order authorizing U.S. support for rebels seeking to depose Assad.

Gulf sources told Reuters that Turkey had set up a secret base to direct vital military and communications aid to Syria's rebels from the city of Adana near the border.

The statement said Turkey had used the camps as “military bases” for terrorists who then headed to Syria to commit crimes.

A Turkish foreign ministry spokesman said: “It is not the first unsupported claim coming from Syria. These speculative claims are not reflecting the truth.”

Mobile and Internet reportedly cut in Aleppo

Meanwhile, mobile phone and Internet services have been cut in Aleppo, Syria’s second city, where a crucial battle is taking place between rebels and the army, the Syrian Observatory for Human Rights said on Thursday.

“Mobile telecommunications services and Internet have been cut off in the city of Aleppo since last night,” it said.

An activist, who asked not to be identified, confirmed that the Internet, landlines and some mobile services were down in the northern city, Syria's commercial hub.

“MTN is down while Syriatel is working. But Syriatel is working only for calls, not the 3G Internet service,” he said, referring to the only mobile providers in the country. “The landlines are also down.”

A Syrian security source in Damascus told AFP that such cuts are “generally the precursor to a major military offensive.”

The rebel Free Syrian Army has said it controls “50 percent” of Aleppo, where the army is bombarding rebel-held areas but has yet to advance on the ground.

The conflict in Aleppo has raged since July 20, with both sides sending in reinforcements for what the security source has predicted will be a protracted battle.

President Bashar al-Assad’s troops meanwhile bombarded the strategic Salaheddine district in Aleppo itself with tank and artillery fire while rebels tried to consolidate their hold on areas they have seized.

In the capital Damascus, troops overran a suburb on Wednesday and killed scores of people, mostly unarmed civilians, residents and activist organizations said.

Fighting rages

The fighting for Syria’s two biggest cities highlights the country’s rapid slide into full-scale civil war 17 months on from the peaceful street protests that marked the start of the anti-Assad uprising.

World powers have watched with mounting concern as diplomatic efforts to find a negotiated solution have faltered and violence that has already claimed an estimated 18,000 lives worsens.

More than 180 people were killed in Syria on Wednesday, 133 of them civilians and 45 of them members of Assad’s forces, according to the opposition Syrian Observatory.

Reuters correspondents heard heavy weapons fire on Thursday morning from Salaheddine in southwest Aleppo, a gateway to the city of 2.5 million people that has been fought over for the past week.

Heavily armed government troops are trying to drive a force of a few thousand rebel fighters from the city in battle whose outcome could be a turning point in the conflict.

Although government forces have made concerted efforts to take Salaheddine, a full-out assault on the city as a whole has yet to take place.

In Damascus, still a government stronghold but a scene of combat in the past two weeks, government troops faced new accusations of atrocities after they overran a suburb on Wednesday.

Syrian state television said “dozens of terrorists and mercenaries surrendered or were killed” when the army raided Jdeidet Artouz and its surrounding farmlands.

In a rallying cry to his troops on Wednesday, Assad said their battle against rebels would decide Syria’s fate.

But his call-to-arms, in a written statement, gave no clues to his whereabouts two weeks after a bomb attack on his inner circle.

Assad, who succeeded his late father Hafez 11 years ago to perpetuate the family's rule of Syria, has not spoken in public since the bombing in Damascus killed four of his close security aides, although he has appeared in recorded clips on television.

His low public profile has fuelled speculation about his grip on power since the attack in which his brother-in-law died.

Some foreign fighters, including militant Islamists, have joined the battle against Assad, who accuses outside powers of financing and arming the insurgents.

Aleppo had long stayed aloof from the uprising but many of its 2.5 million residents are now caught up in battle zones, facing shortages of food, fuel, water and cooking gas. Thousands have fled and hospitals and makeshift clinics can barely cope with casualties after more than a week of combat.

In London, British Prime Minister David Cameron and Russian President Vladimir Putin were to discuss Syria on Thursday.

Britain has strongly criticized Moscow’s refusal to back U.N. Security Council action against the Damascus regime, and the Kremlin said Putin would staunchly defend Russia's position on the crisis.

U.N. spokesman Martin Nesirky stressed on Wednesday that U.N. leader Ban Ki-moon wants united international pressure on both sides.

He said pressure should be brought to bear on “not just the Syrian government forces -- who of course bear the lion's share of the responsibility for what is happening -- but also on the opposition forces, to ensure that they do heed the calls, that they do stop the fighting.”

On Friday, the U.N. General Assembly will vote on a largely symbolic Arab-drafted resolution calling on Assad to stand down.

The United Nations says that some 200,000 of the city’s estimated 2.7 million population have fled their homes, many of them taking refuge in schools and other public buildings.

Three million Syrians need food, crops and livestock assistance, the U.N.’s Food and Agriculture Organization said, citing a survey by the United Nations and the Syrian government.

The FAO said figure included 1.5 million Syrians who “need urgent and immediate food assistance over the next three to six months, especially in areas that have seen the greatest conflict and population displacement.”